Effect on South American CL: This
proposal would overhaul our linear sequence of accipitrid genera.

Background
& New Information & Analysis:The genus Busarellus has traditionally placed
within the buteonine genera of the Accipitridae, but this is clearly not
correct. The relevant Note from our SACC classification is:

17a. Olson
(1982) found morphological evidence that Busarellus may be more closely
related to a group of largely Old World genera (Milvus, Haliastur,
Haliaetus, Ichthyophaga) than to the New World genera with which
is traditionally associated in linear sequences (e.g., Friedmann 1950, Meyer de
Schauensee 1970), and this is reflected in the linear sequence of the AOU
(1998).Genetic data (Griffiths et
al. 2007, Raposo do Amaral et al. 2009) also indicate that it is not closely
related to any buteonine genera, where traditionally place, but rather closer
to kites.SACC
proposal needed.

Olson (1982)
used toe morphology to predict that Busarellus
is not closely related to buteonine hawks but rather to Old World kites.Raposo do Amaral et al.’s (2009)
phylogeny (see proposals 459, 2460) clearly indicated that Busarellus is not
within the buteonines; because their analysis targeted that group, only a few
outgroup taxa were used.Nevertheless, a well-supported node group Busarellus with Geranospiza
and Rostrhamussociabilis to the exclusion of all the buteonines as well as Ictinia, Old World Butastur; and Haliaeetus;
sampling did not include the taxa mentioned by Olson, but regardless, Busarellus cannot be considered
buteonine.The relevant portion of
their tree (from their Fig. 3) is pasted in here:

Therefore, at
present, there is no evidence that Busarellus
is a buteonine hawk.Although which
non-buteonines are actually its closest relatives cannot be determined without
additional taxon sampling, it is clear that it must be moved elsewhere.Griffiths et al. (2007) sampled
extensively outside the buteonines but sequenced only one (nuclear) gene
(RAG-1).Their maximum-likelihood
tree places Busarellus with Butastur and Ictinia; however, support for the structure of this whole region of
the tree is weak to nonexistent, and that further sampling could show it to be
the sister of any of the genera in the tree from Rostrhamus to Geranospiza,
and possibly even others more basal in the group:

Thus, we could
place it anywhere in the current sequence of non-elanine kite genera:

Note that the
RAG-1 tree conflicts strongly with the Raposo do Amaral et al. tree in terms of
which genera are closest to Busarellus:
Rostrhamus or Geranospiza but definitely not Ictinia
in Raposo do Amaral et al., but most likely (statistically) Ictinia or Geranospiza and much less likely Rostrhamus in Griffiths et al.Which one is correct requires additional taxon and gene sampling.If part b (below) is rejected,
arbitrarily placing it after Ictinia
in our current sequence in hopes that the unsupported structure in RAG-1 tree
turns out to be correct would be my recommendation.

We could also
place it next to Geranospiza,
currently between Accipiter and Leucopternis, but that placement of Geranospiza makes little sense in light
of the results of Griffith et al. (2007).This leads to the second part of the proposal: an overhaul of the
sequence of genera

Here I propose
that we change our sequence so that it corresponds more closely with that of
Griffiths et al. (2007), which we already used to move some of the kite genera
(e.g., Elanus and Gampsonyx) to the beginning of the
sequence.My rationale is that (a)
as long as Busarellus must be moved,
and (b) the likely close relatives to Busarellus
are separated by monophyletic groups such as Accipiter + Circus, we
might as well adopt the general structure of the Griffiths et al. tree.This would also place Geranospiza among the other candidate
genera for the sisters to Busarellus
(instead of between Accipiter and the
buteonines).There will always be
questions about trees based on a single gene, but the support for the deep
nodes in the RAG-1 tree are strong, and the groupings themselves are all
sensible.Additional data might
require changes to the sequence, but basing our sequence on the RAG-1 tree
reflects the best data currently available.Finally, the current linear sequence of
groups of genera is based on mostly historical momentum, which is largely a
concoction of antiquated ideas about “primitive” and “advanced” hawks –
therefore, ANY new sequence based on modern data would have more published
support and testable hypotheses than the historical one.

The RAG-1
tree:

and might be
better visualized from their more schematic version:

Adopting the
Griffiths et al. tree would involve one major rearrangement: bringing forward
in the sequence the eagle genera Morphnus,
Harpia, and Spizaetus, thus leaving the buteonines last (see proposals 459 and 460 for the
proposed realignments in those genera).The only other “major” change would be the above-mentioned move of Geranospiza forward to the kites.

Our current
sequence is as follows (with Busarellus
and putative relatives in red):

A sequence consistent
with Griffiths et al. that minimizes the number of changes is (note that
proposals 459 and 460 would affect the buteonine genera Leucopternis through Buteo,
but the group itself would stay intact); taxa whose position is changed are
shown in blue:

Thus, the beginning and
end of the sequence stays relatively stable.The harpy eagles and booted eagles are
brought forward, as is Harpagus slightly and Circus + Accipiter
slightly.The milvine kites, which
would include Rostrhamus through Geranospiza, are all now
together, although whether they form a monophyletic group is questionable from
the RAG-1 tree.The main
accomplishment is bringing Busarellus out of the buteonines, placing it
among its potential relatives.The
proposed new sequence also rescues the harpy eagle types from any association
with the monophyletic buteonines.I
considered moving Harpagus and Rostrhamus (with unproven close
relative Helicolestes) slightly to match the RAG-1 branching pattern,
but there is little or no support for the nodes on that section of the
tree.Tweaks welcomed.

Recommendation: The proposed sequence is consistent with the phylogenetic
hypotheses of Griffiths et al.’s RAG-1 tree, and extricates Busarellus from the buteonines.Pending tweaks, I recommend a YES vote
to incorporate the best phylogenetic data available into our sequence.The vote is broken into two parts:

a) = to move Busarellus out of buteonines
b) = to use proposed sequence above.

Comments
solicited from Fabio Raposo:
“Two important references
may make the difference here. Based on a representative taxonomic sampling
of the family Accipitridae, Lerner & Mindell 2005 recovered
species of Haliaeetus, Ichthyophaga, Haliastur and Milvus as
the closest relatives of the "core" buteonine hawks + Ictinia,
Geranospiza and Rostrhamus (Fig. 1 of that paper), based on two
mitochondrial markers. A smaller taxonomic sampling of the
mitochondrial dataset plus one nuclear intron provides a similar
picture with even better support (Fig. 2). "Kites" seem to represent
an artificial group, since kite genera appear all over their accipitrid tree. So,
it is possible that Geranospiza, Rostrhamus, Ictinia and Butastur
are indeed better thought as buteonine hawks - and Busarellus
and Butastur also seem to be part of this clade (see Lerner et
al. 2008, besides Amaral et al. 2009).

Lerner, H.R., Mindell, D.P.,
2005. Phylogeny of eagles, Old World vultures, and other Accipitridae based on
nuclear and mitochondrial DNA. Molecular Phylogenetics and Evolution 37,
327–346.